Although currently, from an industrial point of view, technical lignin is considered a sub-product which is employed to recover energy by combustion, the valorization of its unique chemical structure is recipient of many efforts from the scientific community. Kraft technology for industrial production of unbleached cellulosic Kraft pulp, produces 70 Mtons/year of lignin-rich byproducts. Such an incredibly abundant source of natural aromatic structures is still poorly exploited in material science due to its variability of structures, chemical composition and polydispersity. The possibility to refine technical lignins into low molar mass fractions presenting high functionality and reproducibility opens new exciting developments in material science. Here we report the relationship between thermo-mechanical properties and chemical structures of well-characterized lignin-based epoxy resins. For this purpose, technical lignins from eucalyptus and spruce, obtained from the Kraft process were used. The choice of lignins was based on the expected differences in molecular structure. The lignins were then refined by solvent fractionation. Subsequent to the refining, three fractions with comparable molecular weights were selected to reduce effects of molar mass on the properties of the final thermoset resins. Consequently, any differences in thermomechanical properties are expected to correlate with molecular structure differences between the lignins. The understanding of the effect of specific structures on the final materials, deliver to the scientific community the unprecedented possibility to design and tune the properties of lignin-based resins.

Unraveling the relationship between structure and material properties in lignin-derived epoxy resins

ACS Spring Meeting 2021

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